I don't play this mode much, but I did yesterday and it happened to me and to 2 of my friends playing with me on different situations. I have to add that it seems exactly like the issue with the cargo on Jetpack Cargo as reported here: https://answers.ea.com/t5/Bug-Reports/JETPACK-CARGO-carrier-players-not-visible-objective-bug/m-p/6644116#M8818
From these reports my guess is an issue with the carriable objectives across the game modes. If anyone has any confirmation of it also happening with those guns used to make the Walkers vulnerable in Galactic Assault, that would be great to narrow even further the reasons for this bug.
But for now I only experienced it in Strike and in Jetpack Cargo.